1. Field of the Invention
This invention relates to a communication controlling method and apparatus, a communication controlling system and a transmission medium, and more particularly to a communication controlling method and apparatus, a communication controlling system and a transmission medium by which control of a plurality of apparatus connected to each other, for example, by a bus which can transmit a control signal in the form of a packet can be performed by a simple command.
2. Description of the Related Art
In recent years, a medium changing device has been developed and a medium exchanging function to a primary device such as a CD player has been defined in the SCSI-2 (small computer system interface 2) standard. The medium changing device is functionally divided into four elements including a medium transfer element, a storage element, a loading/unloading element and a data transfer element. Accordingly, also where a medium exchanging function of a small scale has been implemented, each element is defined by an address of 16-bit length as seen in FIGS. 10 to 12.
Further, movement of a medium can be performed using an instruction which includes a combination of two commands of the Position to Element command illustrated in FIG. 11 and the Move Medium command illustrated in FIG. 10. The Position to Element command is a command to position a designated transport element to the front of a destination element (a position at which the Move Medium command can be executed (to unload a medium from a source element) without any further movement). To the transfer element address, the address of a medium transfer element to be moved by the Position to Element command is designated. To the destination element address, one of the storage element, loading/unloading element, data transfer element and medium transport element is designated.
The Move Medium command is a command for moving a medium which is present in a source element to a destination element. To the transport element address, the address of a medium transport element to be used when the Move Medium command is executed is designated. To the source address or the destination address, one of the storage element, loading/unloading element, data transfer element and medium transport element is designated.
Meanwhile, the Exchange Medium command illustrated in FIG. 12 is a command for exchanging (moving) media between designated elements. A medium present in a source element is transferred to a first destination element, and another medium present in the first destination element is transferred to a second destination element. The same element can be designated as the source element and the second destination element. In this instance, exchanging of media is performed between the source element and the first destination element.
To the transfer element address, the address of a medium transfer element (for example, an arm) to be used when the Exchange Medium command is executed is designated. To each of the source address, first destination address and second destination address, one of the storage element, loading/unloading element, data transfer element and medium transport element is designated.
To the Inv1 (Invert-1), it is designated whether or not a medium (double-sided medium) should be turned upside down when it is moved to the first destination element. To the Inv2 (Invert-2), it is designated whether or not a medium (double-sided medium) should be turned upside down when it is moved to the second destination element.
Here, the data transfer element is a logical definition of a primary device which actually handles a medium to input or output data.
Also where a medium exchanging function is implemented in a small scale in this manner, it is required to define each element with an address of 8-bit length, and the command length is as long as approximately 10 bytes as seen from FIGS. 10 to 12. Therefore, there is a problem in that description of a command is complicated.
Further, in order to effect, for example, movement of a medium, a plurality of commands must be combined. Thus, there is another problem in that such combination of commands is cumbersome.